Disc drives record and reproduce information stored on concentric circular tracks on magnetic discs. The tracks are written and read by magnetic heads which must be accurately positioned over a selected one of the tracks on the surface of the disc. Various methods have been used to position the heads and hold them precisely located over the selected track. The two commonly-used types of head positioning mechanisms are linear and rotary head actuators.
In the second type, which this invention is directed to, the head moves generally radially in order to access the various disc tracks. However, the movement is usually along a segment of a circle. The commonly-known form of rotary actuator includes a head/arm flexure for supporting the transducer, the transducer or read/write head extending out from a pivot to the track position to be accessed. Extending from the pivot to essentially form a V-shaped actuator arm assembly with the head/arm is an actuator arm, which in turn is coupled to a stepper motor. As the stepper motor rotates, the actuator arm assembly rotates about the pivot point, moving the transducer from track to track. Obviously, a highly stable pivot at the end of the actuator arm distal from the stepper motor is absolutely required, so that with the wear caused by time and repeated usage, and the fluctuations caused by changes in operating temperature, the preset position of the transducer relative to a target track and its long term stability over that track is not easily altered. The pivot mechanism must offer high precision, reliability and low mechanical resistance. Further, in the present price-conscious competition in the disc drive market, the pivot mechanism must be easily constructed and assembled.
The pivot mechanisms in the prior art generally include a shaft supporting the juncture of the two arms, i.e. the actuator drive arm and the head arm, two ball bearings, and the required spring retainers preload springs and attachment means coupling the separate elements to the arms.